Transition Metal Silyl Complexes LVI [1]. (CO)4Fe(H)SiR3 and [(CO)4FeSiR3]−– A Density Functional Study on the Influence of the Substituents at Silicon on the Electronic Properties of the Metal Center

Abstract

The effect of the substitution pattern at the silyl ligand in complexes of the type (CO)4Fe(H)SiR 3 and the corresponding anions [(CO)4FeSiR 3]− was investigated by a density functional study. Upon successive substitution of R=H for R=Cl, a contraction of the Fe–Si bond takes place in both types of complexes. The effect of the substitution is much larger in the anionic complexes which is explained by a higher degree of back bonding from the metal center to the SiR 3 ligand. The optimized structures of the complexes are in good agreement with related experimental ones. The changes in electron density at the metal center are also reflected in calculated vibrational frequencies of the CO ligands and the proton affinities of the anionic complexes. An increasing electron withdrawal by the silyl ligand lowers the proton affinity.